Process for exhausting detector tubes



Oct. 25. 1927;;

I 1,646,633 R. T. ST. JAMES" PROCESS FOR zxrmusrme nnwcron TUBES Filed April-10, 1922 may be conveniently dried by passing it through several aciddrier vessels 18 and 19, and I have found that the alternate exhausting and flushing steps should be continued about four times. This is the first or rough pumping stage of the process and the receptacles in this'stage are exhausted at each pumping. operation'to a vacuum of approximatel one-tenth of a millimeter.

. A final flushing of'dry air is given to the receptacles with air, which, in addition to "being passed through the acid driers1 8 and 19, is passed through a final drying vessel "suchas those just mentioned but containlng anhydrous phosphorousnwhich removes the last traces of moisture inthe air and thus makes'it capable of taking up the last traces of moisture in the detector receptacle. In exhausting the last charge 'of flushing air the "vacuum' is carried to approximately 1/100 of a millimeter. I t

' The metallic elements of the device are now connected inmultiple at the external "connectionofthe same (to preclude arcing between elements) and" While enclosed in a maintained vacuum, said elements "are sub-' jected to a high frequency potential, (preferably40,000 volts) one terminal of the potential being the-elements enclosed in the vacuum tube, and the other terminahground, asshown in the drawing. We have thus a condenser effect between the metal elements,- exhausted tube and ground through ordinary atmospheric pressureTThe elements are thus subjected to an electrostatic action of i {a high frequency high voltage.

'T'his step of the-process acts to disrupt and to driveofi' the more readily vaporizable or 'volatilizable elements on the surfaces of the'metal and other parts Within the 'tube.-

The passage of the vapors or gases may be "observed by the fluorescenceresulting from this treatment, which isc'ontinued '(the process of exhaustion being carried on at the same time) until the ffiuorescence'cea'ses and disappears. External heat is then appliedto' the tubes, in any convenient, well known manner as by the coils'13, to drive off such vapors as have condensed upon the inner surfaces of the tubes. A temperature of approximately 600 F. applied to thetubes will generally be sufficient; At this stage the exhaustion is continued to the limits of a mer-f cury condensation pump, that is to say, to the production of an almost perfect, commercially productive vacuum in the tubes.

The so-called hot element of the detector, namely, the filament, is now heated to incandescence by applyin an alternating current to-its terminalsan .a direct current of substantially 220 volts is applied to the cold or plate elementof the detector, the positive terminal being connected to the plate element and the. negative terminal being connected to the filament. The current applied to the filament is adjusted to produce incandescence of the filament slightly above normal,that is to say, above that which 'it should have if used as the lighting element in an incandescent lamp,and until fluorescence 'occurs'between the filament and the plate element. The plate element becomes heated to a point somewhat above the nor mal low temperature which it attains, when the detector is in use, but not to a temperature to occlude allofthevolatiliZable constituents of the plate. This brings about the dislodgment, disruption and volatilization of constituents on the surfaces of the parts within the tubes,- which are less readily vaporizable or volatilizable thanthose already driven off, as heretofore described. The passage from the tubes of the gases or vapors is indicated by fluorescence. The treatment is continued, the gases'or vapors being exhausted as before, for about fifteen (15) minutes, at the end of which period the tubes are again heated externally, to drive off such vaporsor gaseous matters" as may have condensed on the inner surfaces of the tubes. A temperature applied to the tubes of about 550 to 600 F. and continued forabout ten (10) minutes will suffice. 7 In the last treatment, the filament is sublilo jected to a temperature greaterthan it will be subjected to in the normal'use of the detector and the cold element is subjected to a voltage many times above normal. This treatment being continued for thetime mentioned, a great part of the volati'lizableele ments On the parts within the tubes will be disrupted and driven off, but there will be left on themetal partswithinthe-tube, especially the plate, an amou'nt or reservoir of what may be called latent volatilizable or vaporizable constituents, there being enough 'of-such volatilizable constituents remaining,

that the tube will retain its-balance as a soft tube, without'danger of breaking down when-used with the. normal voltages im-" pressed-in operating.

I have found that detectors-where the receptacles or tubes have been exhausted in this manner, will always be. of uniform so ftness; will all operate with a maximum of efliciency for the kind or style of' detector employed; will have a maximum of efficient life;- and' will operate with almost entire absence of all extraneous noisesand tone vibrations. I

I claim as my invention 1. The process of exhausting detector tubes which consists in exhausting and extractlng all moisture from the tube; in then disrupting anddrivlng olf the more easily detachable volatilizable constituents. on the elements of the tube by subjecting them siexternallyheating the tube todrive off c0n-, densation from its inner surface, and then sealing the tube. V I

2; The process of exhausting detector tubes, which consists in cleansing the metal elements of the detector before sealing them in the tube; in' then exhausting the tubes and extracting all moisture therefrom;then

disrupting and driving off the more easily detachable volatilizabl'e constituents on the metal elements by Y subjecting them simultaneously to the electrostatic action of a high frequency high voltage, afterwards applying external heat to drive ofl such cons'tit-- uents as have condensed on the inner'surfaces of the tubes; then heating the filament above normal and at'the same time subjecting the plate element todirectcurrent at high voltage for a predetermined length of time then again externally heating thetubes to drive of]? condensation from their inner surfaces; and then sealing the tubes. 7'

3. The process 1 of exhausting detector tubes, Which consists in cleansing the metal elements to remove all extraneous matter exhausting and extracting all moisture from the tubes by subjectingthem alternately to before sealing them in the tubes; in then exhaustion and flushing'vvith'dried'air; in

then disrupting and vdriving off the more easily detachable volatilizable constituents on the metal elements by sub ecting said elements simultaneously to the electrostatic action at substantially 0,000 volts of high frequency, afterwards applying extenal heat 7 i to drive off such constituents as have condensed on the inner surfaces of the tubes; 1

in then heating the filament by'alternatir g current to incandescence'above normal and subjecting thecplate element to direct current at substantially 220 volts for a prede-. V

termined length of. time, then externally heating the tubes to drive off condensation from their inner surfaces; and then seal ng;

the tubes;

,In testimony that it claimthe sa es-g j as my invention, I affix mysignat-ure this 5th day of April, A. 111922. l V i ROBERT T.;sT. JAMES. 

